Hey Andrew! Welcome to SVS, glad you're here.
I checked out your website. Impressive work for a 17 year old. I see a lot of good foundational stuff you're doing. Julie is right, posing characters would be a great course to start off with. Also, "Breathing Life Into Your Characters" is another good one.
As for posting an image take the url of the image you want to share, like this one:
http://www.andrewgthomas.com/uploads/2/6/9/6/26966605/6433493.png
Then do this: 
And this is what it looks like: